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Intermittent misfiring, doesn't throw codes

Old 12-05-2015, 10:49 PM
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Default Intermittent misfiring, doesn't throw codes

So one day out of the blue my 1998 Cherokee sport started misfiring horribly and it threw a code for cylinder 1 misfire. I let it sit for a day and the check engine light went off by itself, but it still misfires like crazy at any random time, idling or accelerating, but not all the time and nothing in particular seems to cause it . I replaced all the spark wires and plugs and it didn't help. I soaked my distributor cap with it running in the dark and saw arcing, so I figured a cracked distributor was the problem, well today I replaced the cap and rotor and it's still misfiring yet doesn't throw codes. I don't know what to do next besides bringing it to a mechanic
Oh yeah, also I put in a full bottle of decarbonizer or whatever, even though I opened the throttle body and it was perfectly clean. Also if it starts misfiring when I accelerate, it will bog and lose power and I can bring it out of it by pumping the gas. Don't know if that helps diagnose

Last edited by Tbone5466; 12-05-2015 at 11:07 PM. Reason: Misspelling
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Old 12-06-2015, 03:08 AM
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Have a buddy with a '96. Thing was running like crap. He figured tune-up. Replaced wires, cap, rotor, plugs, fuel and air filters. Still ran like crap. Drove him nuts. Finally figured out it was the coolant sensor. The one in the thermostat housing. Not sure if this would apply to a '98 though.
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Old 12-06-2015, 04:47 AM
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1. Pull out the spark plug from cylinder 1 and check gap then check spark.

2. Check fuel to cylinder. Take a squirt bottle to injector seals and if it smooths out then its the seals.

3. Check for vacuum leaks or clogged CCV/PCV line.

4. Check air filter and fuel filter.

5. Check for clogged cat.

6. Check all sensors.

7. Compression test.

hmm..what else?
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Old 12-06-2015, 09:10 AM
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Originally Posted by quneur View Post
1. Pull out the spark plug from cylinder 1 and check gap then check spark.

2. Check fuel to cylinder. Take a squirt bottle to injector seals and if it smooths out then its the seals.

3. Check for vacuum leaks or clogged CCV/PCV line.

4. Check air filter and fuel filter.

5. Check for clogged cat.

6. Check all sensors.

7. Compression test.

hmm..what else?
Air filter and plugs are good, my dad has said that my car smells like it's burning coolant to him, and I have had to fill it periodically as it gets alittle low. Can you elaborate on step 2 because I have no idea what you meant
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Old 12-08-2015, 10:24 AM
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Its a little trick of testing injector seals. A spray bottle of water or (as some have said fuel injection cleaner or starting fluid) used on the outside of the injectors while the car is running. Injector seals made of rubber will dry and crack with age letting air into combustion cylinder. Spraying water (or starting fluid) will temporarily seal any leaks and engine will temporarily run smoother. There are two seals per injector. One for the rail and where it meets the cylinder.

Where is the burning coolant smell coming from? If from inside the cab, it's probably heater core related. If under the hood, then I would test for combustion gases in the coolant. There are kits you can buy at the auto parts store. This I would do immediately before driving again as this would indicate a cracked head or failed head gasket..
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Old 12-11-2015, 10:07 PM
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Originally Posted by Tbone5466 View Post
So one day out of the blue my 1998 Cherokee sport started misfiring horribly and it threw a code for cylinder 1 misfire. I let it sit for a day and the check engine light went off by itself, but it still misfires like crazy at any random time, idling or accelerating, but not all the time and nothing in particular seems to cause it . I replaced all the spark wires and plugs and it didn't help. I soaked my distributor cap with it running in the dark and saw arcing, so I figured a cracked distributor was the problem, well today I replaced the cap and rotor and it's still misfiring yet doesn't throw codes. I don't know what to do next besides bringing it to a mechanic
Oh yeah, also I put in a full bottle of decarbonizer or whatever, even though I opened the throttle body and it was perfectly clean. Also if it starts misfiring when I accelerate, it will bog and lose power and I can bring it out of it by pumping the gas. Don't know if that helps diagnose
Try replacing the IAC valve. They will cause the symptoms of bucking on acceleration etc when they are going out. They will never throw the code until the windings electrically open all the way. Just grab one from the junkyard to try. It is easier to pull the 4 bolts from the TB and change it out then reinstall the TB. That way you can blow it out with some brake cleaner. IACs on jeeps dont like the decarbonizer fed thru the TB, I just had one fail exactly that way after I did the seafoam. Make sure to cross torque the TB or you will have a vacuum leak there.
Don't forget the O ring for the IAC, place it in the housing first and spray lube it and the IAC then press the IAC into the housing.
ebay map and iac for about $9 ea.

Last edited by 97grand4.0; 12-11-2015 at 10:12 PM.
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Old 02-01-2016, 10:00 AM
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UPDATE: solution was bad bank 1 O2 sensor
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